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Blends of different polymer compounds are widely used for organic field-effect transistors. Here, Neher and colleagues show that moderate carrier doping is important to achieve maximum performance in blends of insulating and semiconducting polymers.

The efficiency of organic blends used for photovoltaic applications depends on their ability to convert photoexcited charges into free holes and electrons. It is now demonstrated that the lowermost energetic states formed at the donor/acceptor interface can reach conversion efficiencies close to 100%, and therefore do not behave as traps for charge carriers.

Fitting current–voltage curves of organic solar cells with the Shockley equation often results in artificially high ideality factors. Here, the authors analyse inadequacy of the equation and propose an analytic model, which allows prediction of the efficiency potentials by explicit consideration of charge-carrier mobilities.

A new series of non-fullerene acceptors with asymmetric branched alkyl chains are developed to achieve more than 20% efficiency organic solar cells.

Non-radiative recombination is a critical limiting factor for perovskite solar cell performance. Stolterfoht et al. visualize the various recombination pathways in planar pin cells with photoluminescence imaging and use it to design improved solar cells with 1 cm² areas and ~20% efficiency.

A mismatch between quasi-Fermi level splitting and open-circuit voltage is detrimental to wide bandgap perovskite pin solar cells. Here, through theoretical and experimental approaches, the authors optimize n- and p-type interfaces to achieve open-circuit voltage of 1.29 V and T80 of 3500 h at 85 °C.

Effective transport layers are essential to suppress non-radiative recombination losses. Here, the authors introduce phenylamino-functionalized ortho-carborane as an interfacial layer, and realise inverted perovskite solar cells with efficiency of over 23% and operational stability of T97 = 400 h.

Understating degradation pathways is critical to the development of perovskite photovoltaics. Thiesbrummel et al. show that internal electric field screening induced by ion migration is a dominant contributor to the operational performance loss of perovskite solar cells.

Understanding the mechanism of non-radiative losses in organic photovoltaics is crucial to improve the performance further. Here, the authors use combined device and spectroscopic data to reveal universal model to maximise exciton splitting and charge separation by adjusting the energy of charge transfer state.

It has been commonly believed that the driving force at the donor-acceptor heterojunction is vital to efficient charge separation in organic solar cells. Here Zhong et al. show that the driving force can be as small as 0.05 eV without compromising the charge transfer rate and efficiency.

Strong light-matter coupling can tune exciton properties but its effect in photovoltaics remains unexplored. Here Nikolis et al. show that the photon energy loss from optical gap to open-circuit voltage can be reduced to unprecedented values by embedding organic solar cells in optical microcavities.

Contradictory models are being debated on the dominant pathways of charge generation in organic solar cells. Here Kurpiers et al. determine the activation energy for this fundamental process and reveal that the main channel is via thermalized charge transfer states instead of hot exciton dissociation.

The open circuit voltage, short circuit current and fill factor determine the conversion efficiency of organic solar cells, yet the fill factor is not well understood. Here, Bartesaghi et al. demonstrate the fill-factor dependence on the ratio of the recombination and extraction rates of free charges.

The conversion efficiency of organic solar cells suffers from their low open-circuit voltages. Here, the authors expose a link between electron-vibrations coupling and non-radiative recombinations, derive a new limit for the efficiency of organic solar cells, and redefine their optimal optical gap.

Designing gentle sinusoidal nanotextures enables the realization of high-efficiency perovskite–silicon solar cells

Loss of Trem2 function increases early amyloidogenesis by preventing microglial activation and clustering around amyloid seeds. As a consequence of reduced microglial ApoE production in the absence of Trem2 function, amyloid plaques contain less ApoE.

The performance of organic semiconductor devices depends heavily on molecular parameters. Here, Schwarze et al. point out that the molecular quadrupole moment largely influences device energy levels and show how quadrupole moments can reduce the energy barrier for charge generation in solar cells.

Molecular orientation profoundly affects the performance of donor-acceptor heterojunctions, whilst it has remained challenging to investigate the detail. Using a controllable interface, Ran et al. show that the edge-on geometries improve charge generation at the cost of non-radiative recombination loss.

Charge-transfer states with comparable recombination and charge-splitting rates are shown to be a key ingredient for donor–acceptor organic blends that perform well in both light-emitting and photovoltaic applications.

Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. This Perspective article highlights tandem solar cells based on a wide-gap perovskite and a narrow-gap organic subcell, which could achieve efficiencies beyond 30% and can be produced without large carbon emissions.

Organic solar cells, despite their high power conversion efficiencies, suffer from open circuit voltage losses making them less appealing in terms of applications. Here, the authors, supported with experimental data on small molecule photovoltaic cells, relate open circuit voltage to photovoltaic gap, charge-transfer state energy, and donor-acceptor interfacial morphology.